The present invention relates generally to fibre channel transmissions. More particularly, the present invention relates to a fibre channel port adapter that connects to an open system and allows the multi-protocol channel switch to act as a part of the fabric topology.
Mainframes, super computers, mass storage systems, workstations and very high-resolution display subsystems are frequently connected together to facilitate file and resource sharing. Common networks and channels used for these types of connections oftentimes introduce a communications bottleneck, especially in cases where the data is in a large file format typical of graphically-based applications.
There are two basic types of data communications connections between processors, and between a processor and peripherals. A xe2x80x9cchannelxe2x80x9d provides a direct or switched point-to-point connection between communicating devices. The channel""s primary task is merely to transport data at the highest possible data rate with the least amount of delay. Channels typically perform simple error correction in hardware. A xe2x80x9cnetwork,xe2x80x9d by contrast, is an aggregation of distributed nodes (e.g., workstations, mass storage units) with its own protocol that supports interaction among these nodes. Typically, each node contends for the transmission medium, and each node must be capable of recognizing error conditions on the network and must provide the error management required to recover from the error conditions.
One type of communications interconnect that has been developed is fibre channel. The fibre channel protocol was developed and adopted as the American National Standard for Information Systems (ANSI). See Fibre Channel Physical and Signaling Interface, Revision 4.3, American National Standard for Information Systems (ANSI) (1994) for a detailed discussion of the fibre channel standard. Briefly, fibre channel is a switched protocol that allows concurrent communication among workstations, super computers and various peripherals. The total bandwidth provided by fibre channel network can scale to the order of a terabit per second. A fibre channel link is capable of transmitting frames at rates exceeding 1 gigabit per second in both directions simultaneously. It is also able to transport commands and data according to existing protocols such as Internet protocol (IP), small computer system interface (SCSI), high performance parallel interface (HIPPI) and intelligent peripheral interface (IPI) over both optical fibre and copper cable.
FIG. 1 illustrates a variable-length frame 11 as described by the fibre channel standard. The variable-length frame 11 comprises a 4-byte start-of-frame (SOF) indicator 12, which is a particular binary sequence indicative of the beginning of the frame 11. The SOF indicator 12 is followed by a 24-byte header 14, which generally specifies, among other things, the frame source address and destination address as well as whether the frame 11 is either control information or actual data. The header 14 is followed by a field of variable-length data 16. The length of the data 16 is 0 to 2112 bytes. The data 16 is followed successively by a 4-byte CRC (cyclical redundancy check) code 17 for error detection, and by a 4 byte end-of-frame (EOF) indicator 18. The frame 11 of FIG. 1 is much more flexible than a fixed frame and provides for higher performance by accommodating the specific needs of specific applications.
FIG. 2 illustrates a block diagram of representative fibre channel architecture in a fibre channel network 100. A workstation 120, a mainframe 122 and a super computer 124 are interconnected with various subsystems (e.g., a tape subsystem 126, a disk subsystem 128, and a display subsystem 130) via a fibre channel fabric 110 (i.e. a collection of fibre channel switches). The fabric 110 is an entity that interconnects various node-ports (N-ports) 140 and their associated workstations, mainframes and peripherals attached to the fabric 110 through the F-ports 142. The essential function of the fabric 110 is to receive frames of data from a source N-port and, using a first protocol, route the frames to a destination N-port. The first protocol is, e.g., the fibre channel protocol.
Essentially, the fibre channel is a channel-network hybrid, containing enough network features to provide the needed connectivity, distance and protocol multiplexing, and enough channel features to retain simplicity, repeatable performance and reliable delivery. Fibre channel allows for an active, intelligent interconnection scheme, known as a xe2x80x9cfabric,xe2x80x9d or single fibre channel switch to connect devices. The fabric includes a plurality of fabric-ports (F-ports) that provide for interconnection and frame transfer between a plurality of node-ports (N-ports) attached to associated devices that may include workstations, super computers and/or peripherals. The fabric has the capability of routing frames based upon information contained within the frames. The N-port manages the simple point-to-point connection between itself and the fabric. The type of N-port and associated device dictates the rate that the N-port transmits and receives data to and from the fabric. Transmission is isolated from the control protocol so that different topologies (e.g., point-to-point links, rings, cross point switches) can be implemented.
The fibre channel industry standard also provides for several different types of data transfers. A class 1 transfer requires circuit switching, i.e., a reserved data path through the network switch, and generally involves the transfer of more than one frame, oftentimes numerous frames, between two identified network elements. In contrast, a class 2 transfer requires allocation of a path through the network switch for each transfer of a single frame from one network element to another.
With the advent of widespread use of fibre channel protocols, it has become an issue whether directors that could accept only native Enterprise System Connection Architecture (ESCON(copyright)) connections should be replaced or refurbished so as to accommodate fibre channel signals. That is, the market has a need to transfer from ESCON to fibre channel since many users have a product that was originally designed for one utility (ESCON) and now have a need for greater functionality. Preservation of serial number is very important in this industry (ie. as a capital asset) and there is a lot of value to a product or method that is capable of sending and receiving both ESCON and fibre channel data in same switch. Thus, it is desirable to obtain a multi-protocol channel switch that provides both a true ESCON traffic traversing switch as well as a true fibre channel traffic traversing switch, wherein frames from one protocol are never intermixed with any other protocol.
This was previously thought to be difficult, inter alia, because in ESCON switches, the part of the switch that houses operating code is generally completely taken up; that is, it was thought that there was no room to store code for the new processor type. High availability systems require nondisruptive code load. In addition, in order to modify ESCON switches to accept fibre channel data, it was believed that adaptations of ESCON would disrupt the fibre channel transmission.
Accordingly, an embodiment of a fibre channel port adapter (FCPA) can be installed into a multi-protocol channel switch. The FCPA connects to the open system fibre channel standard and allows the multi-protocol channel switch to act as a part of the fabric topology in the fibre channel standard. This permits devices using fibre channel, called N_Ports, or NL_Ports, to utilize the multi-protocol channel switch through one FCPA or multiple FCPAs and implement a fabric topology. This topology allows an xe2x80x9cany-to-anyxe2x80x9d connection between devices using fibre channel. This any-to-any connection is provided through one or more FCPAs, interconnected through a crosspoint switch (CPSW) of the multi-protocol channel switch.
Fibre channel is an open standard, and the FCPA allows the switched (fabric) topology to utilize the CPSW of the multi-protocol channel switch and provide this open system among FCPAs, independent of ESCON related interfaces in the multi-protocol channel switch.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.